Driving mechanism for oscillating shafts



Jan. 10, 1939. W s, LOWE DRIVING MECHANISM FOR OSCILLATING SHAFTS Filed May 4, 1937 2 Sheets-Sheet l Inventor: WIHIam S. Lowe Hi Attorney.

I w. 4 I.

W. S. LOWE Jam. 16, 1939.

DRIVING MECHANISM FOR OSCILLATING SHAFTS Filed May 4, 1957 2 Sheets-Sheet 2 Inventor": William 3. Low

HIS Attorney.

Patented Jan. 10, 1939 UNITED STAT PATENT OFFICE DRIVING MECHANISM FOR OSCILLA'IING SHAFTS York Application May 4, 1937, Serial No. 140,627

Claims.

The present invention relates to driving mechanisms of the type having a vertical oscillating shaft journaled in a sleeve bearing. One use of such mechanisms is in domestic washing ma- 5 chines Where the vertical shaft is used to drive the agitator.

The object of my invention is to provide an improved construction in driving mechanisms of this type which will prevent the pumping of oil through the space between the oscillating shaft and the sleeve bearing.

In the accompanying drawings, Fig. 1 is a fragmentary elevation of a washing machine hav-- ing a driving mechanism embodying my invention in section along lines l-l of Fig. 2; Fig. 2 is a top plan view in section along lines 2-2 of Fig. 1; Fig. 3 is a perspective view of the guide for the reciprocating rack; Fig. 4 is a sectional view taken on line 44 of Fig. 1; Fig. 5 is a sectional view taken on line 55 of Fig. 2; Fig. 6 is a diagrammatic view showing the sidewise movement of the oscillating shaft in the sleeve bearing; Fig. '7 is a diagrammatic view of the lower end of the oscillating shaft illustrating the manner in which the shaft tends to pump lubricant upward through the space between the shaft and the sleeve bearing; and Fig. 8 is a sectional elevation of a modification having a seal above the bearing as an additional precaution against the leakage of lubricant.

Referring to the drawings, I have shown my invention applied to the driving mechanism for washing machines shown in Patent No. 2,064,653, Forstrom, December 15, 1936. In this construction the tub I is supported at the center by a tubular post 2 which projects through a central opening in the bottom of the tub. The tub rests on a flange 4 on the post 2 and is clamped between the flange and a nut 5 which is threaded on the post. Suitable gaskets 6 are arranged between the tub and the flange 4 and the nut 5 to prevent leakage. The lower end of the post 2 is secured to the top of the gear casing l and is supported thereby. The gear casing extends diametrically across and is bolted at either end to the depending sides of a cylindrie cal skirt 8. Legs 9 for supporting the washing machine are secured to the skirt 8. The gear casing braces the skirt il'and provides a rigid central support for the tub. The outer edge of the tub is tightly held against a rubber cushion It: on the upper edge of the skirt 8. This provides additional support for the tub. The, lower end of the tub projects within and is wedged 55 aga nst the upper rim of the skirt. This increases the lateral rigidity of the skirt and allows the use of lighter material for the skirt.

A vertical shaft II for driving an agitator [2 extends upwardly through the post and is supported by a suitable combined sleeve and thrust bearing (not shown) at the upper end of the post. The agitator has a depending tubular portion which extends downwardly around the post. A collar [3 which is secured to the agitator at the lower end guides the movement of the agitator. The lower end of the agitator shaft II. is carried in a sleeve bearing l4 in the upper wall of the gear casing l. A chamber I5 is provided above the bearing 14- to collect lubricant which may be carried above the bearing. This lubricant is returned to the gear casing through a well or groove lid in the top wall of the gear casing. The well has an opening [512 through which the lubricant flows. The opening is located so that it is always above the level of the lubricant in the gear ca sing regardless of the position of the gear casing. The agitator shaft ll extends within the gear casing I and has a pinion l6 keyed to the lower end which is adapted to mesh with a reciprocating rack I! to cause oscillation of the agitator. The left end of the rack is provided with a crank pin [8 which is rotatable in a bearing eccentrically located in a worm wheel 19. The worm wheel is keyed to the lower end of a vertical shaft 20 which is jcurnaled in the bearing 2| in a tubular wringer post 22. The upward thrust of the worm gear is taken by the lower edges of the bearing 2| which serves as a thrust bearing. The wringer post is clamped to the upper wall of the gear casing by a split clamp 23 integral with the upper wall of the gear casing. The worm wheel i9 is rotated by a worm 24 which is driven by an electric motor 25 carried on the gear casing by rubber rings 26 clamped to supports 21. An intermediate shaft 28 is connected between the motor shaft 29 and the worm shaft 39 by flexible couplings 3|. A thrust ball 32 is provided at the end of the worm shaft 30. The: thrust ball is adjusted by a screw plug 33.. With this arrangement, the worm wheel [9 is continuously rotated in one direction by the motor, and the crank pin i8, bearing in the worm wheel, causes the rack ii to be reciprocated. The body of the rack ii is offset and rigid so that although the end of the rack carrying the crank pin I8 is below the teeth of the worm wheel IS, the teeth of the. rack and the bearing of crank pin H! are in line with the teeth of the worm wheel ISI. This reduces the load on the bearings of the shaft 20 and eliminates vertical forces in the rack thrust which would have a tendency to cause slaps resulting in objectionable noises.

The reciprocating movement of the rack IT is guided by a guide E ia shown in Fig. 3. The guide has flanges 34 which extend over the upper and lower sides of the rack. Secured to the lower flanges is a tongue 35 which slides in a groove on the under side of the rack and holds the rack in the guide. From the rear edge of the guide extend ears 36 which are pivoted on the inner end of the plunger 37 slidable in the walls of the gear casing l. The ears 36 support the rack on the plunger and the pivotal connection between the ears 36 and the plunger permit pivotal movement of the guide during the reciprocating movement of the rack. The outer end of the plunger 37 projects through the side wall of the gear casing, and the plunger is urged outward by a spring 38 arranged between the gear casing and the outer end of the plunger. The spring 38 thereby tends to move the plunger to a position in which the rack is out of mesh with the pinion. The plunger is moved inwardly to the position shown in Fig. 2 by means of a control lever 39 pivoted on a bracket 40 secured to the outside of the gear casing. The end of the control lever is provided with a cam M which engages a set screw 42 threaded into the end of the plunger 3?. When the control lever is in the position shown in full lines in Fig. 2, the rack is pressed into engagement with the pinion. When the control lever is in the position shown in dotted lines, the spring 38 moves the plunger outwardly, thereby moving the rack out of engagement with the pinion.

On the under side of the crank pin I8 is a pin 42a, which is pressed by a spring 43 against the cover 44 of the gear casing. The friction between the pin 42a and the cover of the gear casing opposes the reciprocating movement of the rack and thereby tends to prevent overtravel of the reciprocating rack and reduces the back-lash between the worm and the worm gear.

, The friction between the pin 42a and the cover of the gear casing also tends to retard the rotation of the crank pin and thereby tends to hold the crank pin against its bearing in the worm wheel during all parts of the reciprocating movement of the rack and particularly during the reversal of the reciprocating movement of the rack. The frictional force between the crank pin and its bearing is always in the same direction, and causes the rack to bear against the back of the guide 34a, thus preventing wobbling of the rack in the guide and eliminating noise from this source. When the rack is being reciprocated, it is continuously held against the back of the guide 3 3a and the tongue 35 is then merely a means for making sure that the rack is pulled out of mesh with the pinion in case of binding between some of the parts. The spring pin 42a also prevents the crank pin is falling from its bearing in the worm wheel E9. The pin 4211 supports the wringer shaft 29, eliminating the need for a thrust bearing to support the gravity component of the worm gear and shaft thrust. It would be inconvenient to provide such a thrust bearing at the bottom of the wringer shaft, and if the thrust bearing were provided at the top of the wringer shaft, it would be difficult to prevent excessive play between the bearing and the shaft due to expansion and contraction of the shaft and the Wringer post. The pin 42a also prevents vertical movement of the shaft due to variations in the vertical reaction between the worm 24 and the worm wheel I9 caused by the variable load taken by the reciprocating rack. If this vertical movement were not prevented by the pin 42a it would produce a gear noise due to the change in mesh between the worm 24 and the worm wheel I 9, and it would also produce a knock on the thrust bearing used to take the variable upward thrust of the worm gear.

When the bearing I4 is a plain sleeve bearing a considerable quantity of lubricant is forced upward through the bearing during the oscillation of the shaft II. For this reason it has been necessary to provide a passage such as the well i5a in order to return this lubricant to the gear casing, otherwise, the lubricant may overflow the top of the gear casing. Since the shaft II is normally oscillated at the rate of about sixty complete oscillations per minute, each oscillation being through an angle of the order of 180 degrees, there is no readily apparent reason why the lubricant should be forced upward through the bearing while the shaft is oscillating. The lubricant could not be forced upward through the bearing because of the difierence in pressure between the inside and the outside of the gear casing since these pressures are the same due to the vent I512. Capillary action could not be wholly the cause of this leakage since the lubricant is not forced through the bearing while the shaft is stationary. It, therefore, seems clear that the forcing of lubricant upward through the sleeve bearing must be due to a pumping action. During the oscillation of the shaft the shaft may have four types of motion: (1) an up and down motion due to end play; (2) an oscillating motion, through an arc of the order of 180 degrees, the velocity and acceleration being different in each half cycle of the oscillation;

(3) a tipping motion which is indicated diagrammatically in Figs. 6 and 7; and (4) a sidewise motion of the shaft in the bearing. Tests indicate that the pumping action is due mainly to causes (2), (3), and (4). The up and down movement of the shaft is not present in a properly designed construction. The tipping action illustrated diagrammatically in Figs. Band 7 is in effect a pivotal movement of the shaft about the sleeve bearing 45 at the upper end of the post 2. This action is permitted by the clearance in the sleeve bearing it which is greatly exaggerated in Fig. 6 and somewhat less exaggerated in Fig. 7 for the purpose of illustration. Fig. '7 shows the position of the shaft when the rack is traveling to the right. In moving to this position, lubricant is sucked in at 46 and forced out at 41. When the rack reverses and moves toward the left, the lubricant which was sucked in at it is forced out at 48 and lubricant is sucked in at 59. The tilting of the shaft, therefore, produces a pumping action which tends to force the lubricant upward through the bearing. It has been found that a sidewise motion of the shaft in the bearing without any tilting will pro duce the same pumping action.- A sidewise movement of the shaft can result from the thrust along the center-line of the reciprocating rack. It can also result from the variation in the force exerted by the teeth of the rack on the teeth of the pinion. This force varies in magnitude with the angular position of the pinion and is in general perpendicular to the center-line of the rack.

The pumping action from all causes is eliminated by providing vertical slots 50 in the bearing surface of the bearing. Two of the slots are arranged on the center-line of the reciprocating movement of the rack and the other two slots are equally spaced therebetween. These slots prevent the building up of pressure between the shaft and the bearing during the tilting or sidewise movement of the shaft and thereby prevent the pumping of the lubricant. That is, instead of being forced upward by the tilting of the shaft or the sidewise movement of the shaft toward the bearing, the lubricant is forced into the slots be and drains into the gear casing. The slots 5!! also serve to scrape excess lubricant from the shaft and thereby prevent any pumping action due to changes in the angular velocity of the shaft. Although the slots have been illustrated in the bearings, it is obvious that these slots could also be placed in the shaft. The slots are shown as vertical and there is, therefore, no tendency for lubricant to be forced upward in the slots due to centrifugal action. The slots need not be absolutely vertical, it merely being essential that the slots have insuflicient inclination to cause lubricant to be forced upward therein by centrifugal action.

In the construction shown in Fig. 8 a seal has been provided as an additional precaution to prevent leakage of lubricant. This seal is not necessary. The seal comprises a bearing and sealing washers 52 which are forced against the lower end thereof by a compression spring 53 arranged between the upper end of the bearing it and a washer 54. With this arrangement a space is provided between the upper end of the bearing and the seal in which lubricant can oollect. Any lubricant collecting in this space will drain to the gear casing through the slots 50.

. What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, a casing containing lubricant, a shaft extending through the top wall of the casing, a sleeve bearing for the shaft in the top wall of the casing, means including a reoip rocating member within the casing for oscillating the shaft, and an axially extending groove in the sleeve bearing for preventing the pumping of lubricant from the casing through the space between the shaft and the bearing, the lower end of said groove communicating with the interior of the casing and the upper end of the groove communicating with the exterior of the casing.

2. In combination, a casing containing lubricant, a sleeve bearing carried by a wall of the casing, a shaft extending through the bearing, means including a reciprocating member within the casing for oscillating the shaft, and an axially extending groove in said bearing for preventing the pumping of lubricant from the casing through the space between the shaft and the bearing, the lower end of said groove communicating with the interior of the casing and the upper end of the groove communicating with the exterior of the casing.

3. In combination, a casing containing lubricant, a sleeve bearing carried by a Wall of the casing, a shaft extending through the bearing, means including a reciprocating member within the casing for oscillating the shaft, axially extending grooves in said bearing arranged in line with the reciprocal movement of said member, and axially extending grooves in said bearing arranged intermediate said first grooves, the lower ends of said grooves communicating with the interior of the casing and the upper ends of the grooves communicating with the exterior of the casing.

4. In combination, bearing surfaces comprising a sleeve bearing and a shaft extending through the bearing, means for effecting oscillation of the shaft and bearing relative to each other, and an axially extending groove in one of the bearing surfaces for relieving the pressure of the lubricant between the shaft and the bearing whereby pumping of the lubricant through the space between the shaft and the bearing is prevented.

5. In combination, a stationary bearing surface, a member bearing on said surface, means for reciprocating said member relative to said surface, the reciprocal movement being accompanied by movement of said member toward and away from said surface, and a groove in the said surface extending transversely to the reciprocal movement for relieving the pressure of lubricant whereby pumping of lubricant between the said member and said surface in the direction of said groove is prevented.

WILLIAM S. LOWE. 

